Formulas: Compression Flange Local Buckling

Equation F3-1

M_{n}=M_{p}-\left(M_{p}-0.7 F_{y} S_{x}\right)\left(\frac{\lambda-\lambda_{p f}}{\lambda_{r f}-\lambda_{p f}}\right)

M_{n}=\frac{0.9 E k_{c} S_{x}}{\lambda^{2}}

where

$k_{c}=\frac{4}{\sqrt{h / t_{w}}}$ and shall not be taken as less than 0.35 nor greater than 0.76 for calculation purposes

$h=$ distance as defined in Section B4.1b, in. (mm)

$t_{w}=$ thickness of the web, in. (mm)

$\lambda=\frac{b_{f}}{2 t_{f}}$

$b_{f}=$ width of the flange, in. (mm)

$t_{f} \quad$ = thickness of the flange, in. (mm)

$k_{c}=\frac{4}{\sqrt{h / t_{w}}}$ and shall not be taken as less than 0.35 nor greater than 0.76 for calculation purposes

k_{c}=\frac{4}{\sqrt{h / t_{w}}}

\lambda=\frac{b_{f}}{2 t_{f}}

$\lambda_{r f}=\lambda_{r}$ , the limiting width-to-thickness ratio for a noncompact flange as defined in Table B4.1b

\lambda_{r f}=\lambda_{r}